const {StringDecoder} = require('string_decoder')
const decoder = new StringDecoder('utf8')
const buf = Buffer.from('中文字符串！理你理你')

for (let i = 0; i < buf.length; i += 5) {
    const b = Buffer.allocUnsafe(5)
    buf.copy(b, 0, i);
    console.log(b.toString())
}

for (let i = 0; i < buf.length; i += 5) {
    const b = Buffer.allocUnsafe(5)
    buf.copy(b, 0, i);
    console.log(decoder.write(b))
}
